Control apparatus



Dec. 8, 1942. H. s. JONES 2,304,641

CONTROL APPARATUS Filed May 4, 1940 HARRY S. JONES 9 BY wi/MW" ATTORNEY.

' of distinguishing between steady Patented Dec. 8, 41942 2,304,641 CONTROL APPARATUS Harry S. Jones, Philade Instrument The Brown lphia, Pa., assignor to Company, Philadelphia,

Pa., a corporation of Pennsylvania Application May 4, 1940, Serial No. 333,337

16 Claims.

The present invention relates to light-sensitive control systems.

An object of the invention is to provide a light-sensitive control system which is capable sources of illumination and fluctuating sources of illumination.

A specific object of the invention is to provide ran improved safety control system for a fuel burner which responds in one sense to the presence of a flame at said burner and responds in another sense to the absence of flame at said burneru Another specific object of the invention is to provide a safety control system for a fuel burner which relies in its operation upon the characteristic fluctuation in intensity of illumination of a fuel burner flame.

A further specific object of the invention is to provide a safety control system for a fuel burner which utilizes a light-sensitive device, exposed to the fuel burner llame, as the flame responsive element and which is insensitive to light radiating frorn the walls of the fuel burner combustion chamber.

A still further specific object of the invention is to provide a safety control system for a fuel burner which utilizes a light-sensitive device, exposed to the fuel burner llame, as the flame responsive element and in which the need of filters or specially designed optical systems are not required.

`A further specific object of the invention is to provide a safety control system for a fuel burner Awhich utilizes a light-sensitive device exposed to the fuel burner llame as the flame responsiver element, which light-sensitive device may be exposed to light emanating from an area `including substantially all Aof the fuel burner flame whereby critical focussing adjustments are unnecessary. l

Light-sensitive safety control systems for fuel burners have heretofore been proposed inthe art. These prior art systems were provided with e. light-sensitive device, such las a photocell, which was simply exposed tothe interior of the combustion chamber. Such systems did not prove satisfactory, however, in that they frequently failed to respond properly upon extinguishment of the flame because the glowing walls of the combustion chamber provided sufficient illumination to keep the light-sensitive device energized. The fuel supply valves consequently were allowed to remain open even though the flame Cil had become extinguished and as a result dis-4 astrous explosions usually followed.

Attempts were subsequently made in the prior art to overcome such defective operation by providing a light filter between the light-sensitive device and the combustion chamber, which light filter was so chosen and designed that only light from the flame was transmitted to the light sensitive device. These improved systemsl also were usually provided with an especially designed critical optical system for focussing the lightsensitive device on a brilliant spot in the flame to prevent the transmission of light to the lightsensitive device from other parts within the combustion chamber, for example, from the walls therein. These expedients, however, have the disadvantage that they cut down the amount of light reaching the light-sensitive device and thereby decrease the sensitivity of the system and furthermore arel expensive. The use of a special optical system not, only further increases the cost appreciably but renders the system extremely delicate and critical of adjustment.

The disadvantages of the prior art systems have been overcome by the system of my present invention in which advantage is taken of the fluctuating characteristic of the light emanating from a fuel burner flame. The light emanating from the walls of the burner is steady compared with the light given off by the flame and therefore the presence or absence of a flame is readily detected by the system of my present invention without requiring the use of specially designed filters and optical systems.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a. part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawing and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

The single ligure of the drawing shows a fuel burner having a combustion chamber l which is supplied with gas through a conduit 2 in which an electrically operated or other suitable valve 3 is providedrfor controlling the ilow of gas to the chamber l.

A pilot burner 4 is provided which is controlled by an electrically operated or other suitable valve 5, and means are provided for igniting the pilotI flame including a pair of electrodes 6 which are connected to the terminals of a secondary winding 1 of anignition transformer I having a primary winding 9 which is adapted to be energized from the alternating current supply lines L1 and L.

The fuel valve operating circuit of my control system is controlled by means of a thermostat I9 which may be located in a room or space to be heated. The thermostat III may be of any suitable construction and includes a bimetallic element connected by means of conductor I2 to line L2, and a contact blade I3 adapted to engage a stationary contact I4 which is connected to line L1 through a thermal switch I5 and windingr i6 of a transformer I1.

The thermal switch I is preferably of the form disclosed in the Patent v1,958,081 issued to F. S. Denison May 8, 1934. As shown more or less diagrammatically in the drawing, this switch comprises a stationary arm |8 and a movable arm I9 biased for movement away from arm I8 but normally held in engagement with the latter by means of a bimetallic element 20. Element is rigidly secured at one end to a block 2| and is arranged to be heated by a coil 22 when the latter is energized through a circuit which will later be described. Upon energization of coil 22 for a predetermined period of time, element 20 will be warped sumciently in the clockwise direction to permit arm I9 acting under spring or other bias to separate from switch arm I8 H thereby interrupting the circuit including thermostat I 0. The switch I5 will remain locked in this position until manually returned to its normal closed position.

The transformer I1 which supplies power for the control system comprises the primary winding I6, and secondary windings 23, 24 and 25. Secondary winding 23 is used to energize the heater filament-s 26, 21, 28 and 29, of electric discharge devices 30, 3|, 32 Aand 33, respectively. Secondary Winding 24 supplies energy to the discharge device 30 which is shown as a triode and is operated as a rectifier to establish a continuous potential across a. resistor 34 of the correct polarity to render terminal thereof positive with respect to terminal 36. Triode 39 comprises an anode 31, a control electrode 38, a cathode 39, and the heater filament 26. Control electrode 38 is connected to cathode 39 so that the device acts substantially as a diode. The rectifier circuit may be traced from the upper terminal of Winding 24, as it appears in the drawing, to anode 31, cathode 39, resistor 34, across which a condenser 40 is connected, and a conductor 4| back to the lower terminal of winding 24.

A conductor 42, connected to positive terminal 35 of resistor 34, serves as a positive supply line for the electric discharge devices 3| and 32. A conductor 43, connected to a tap at a suitable point on resistor 34, serves as a negative supply line. The discharge device 3| is shown as a triode, comprising an anode 44, a control electrode 45, a cathode 46, and the heater filament 21. The discharge device 32 is shown as a pentode, comprising an anode 41, a suppressor electrode 48, a screen electrode 49, a control electrode 50, a cathode 5|, and the heater filament 28. The output circuit of discharge device 3| may be traced from positive supply line 42 through a resistor 52, across which a condenser 53 is connected, anode, 44, and cathode 46 to the negative line 43. Control electrode is normally biased sumciently negative to limit the flow of current in the output circuit of triode 3| to an insignificant value, this bias being obtained from that part of resistor 34 between the negative terminal 38 and the point of engagement of conductor 43 therewith. This biasing connection may be traced from cathode 45, through conductor 43, resistor 34, terminal 36, and a protective resistor 54 to control electrode 45. The input circuit of triode 3| also includes a condenser 55 connected between control electrode 45 and conductor 43, and a condenser 55 connected between control electrode 45 and anode 41 of discharge device 32. The condenser 53 serves to couple the output circuit of pentode 32 with the input circuit of triode 3|.v Condenser 55 is employed to by-pass undesirable high frequencies which might otherwise affect the input circuit of triode 3|.

The output circuit of pentode 32 may be traced from the positive supply line 42 through resistors 51 and 58, anode 41 and cathode 5| to the negative supply line 43. A filtering condenser 51A is connected between the common terminal of resistors 51 and 58 and the conductor 43. Suppressor electrode 48 is connected to cathode 5|. The input circuit of pentode 32 includes a resistor 59 and a condenser 60 connected in parallel between control electrode 58 and conductor 43. The connection of control electrode 50 and cathode 5| through resistor 59 serves to render pentode 32 normally conductive. Condenser 69 functions as a by-pass condenser, similarly to condenser 55. The input circuit of pentode 32 also includes a branch which may be traced from the positive line 42, through a resistor 6I, a lightresponsive device 62, illustrated as a photo-electric cell, and a resistor 63 to the negative line 43. The common terminal of resistor 6I and cell 62 is connected to screen electrode 49 of pentode 32, and to conductor 43 through a filtering condenser 64. The common terminal of resistor 53 and cell 62 is connected to control electrode 59 through a coupling condenser 35.

The photo-electric cell 62 is mounted in any convenient manner outside an opening 66 in the wall of combustion chamber I, so as to be exposed to light emanating therefrom. A lens 61 may be provided so as to concentrate the rays from a large area within the chamber I upon the cell 62.

When no flame exists within the chamber I. the light if any, falling upon the photo-electric cell 62, is relatively steady, so that the resistance o f the cell and hence the current owing through it is substantially constant. There is then no transfer of energy through condenser 65 and the input circuit of pentode 32 accordingly is unaffected by the condition of the photo-electric cell 62. The output current of pentode 32, therefore, remains substantially constant, and consequently no transfer of energy is effected through condenser 56 to the input circuit of triode 3|. Under this condition the triode 3| is maintained non-conductive.

When a flame is burning within the chamber I, however, the light falling upon photo-electric cell 62 will not be steady but will flicker, that is, fluctuate in intensity, and as a result the conductivity of the photo-electric cell 52 will fluctuate in a corresponding manner. Such fluctuations in the conductivity of photo-electrical cell 62 produces similar fluctuations in the flow of current through resistance 63 and thereby produces a fluctuating potential drop across the latter. The fiuctuations in the potential drop across I resistance 53 are transmitted by condenser 65 and produce corresponding fluctuations in the potential of the control electrode 59 of discharge l device 3| conductive to produce a device 32 relatively to the potential of cathode 5I. These fluctuations in potential applied to the input circuit of the discharge device 32 are amplifled thereby and the amplified fluctuations are applied through the condenser 56 to the input circuit of discharge device 3l. The discharge thereupon is intermittently rendered fluctuating potential drop across resistance 52 which is smoothed out by the condenser 53. The potential drop across resistance 52 accordingly is substantially steady and is employed to control the flow of current in the output circuit of the electric discharge device 33 and thereby the operation of the valves 3 and 5,

which control the supply of fuel to the chamber I, through means to be described.

It will be noted from the foregoing description of the circuit operation that the circuit operates to produce a potential drop across resistance 52 in response to the subjection of the photoelec- M .tric cell 62 of a flickering or fluctuating source of light and that the circuit is unresponsive to the subjection of the photoelectric cell 62 to a steady source of light.

The discharge device 33 is shown as a triode and includes an anode 68, a control electrode 69 and a cathode 18 in addition to the heater filament 29 referred to hereinbefore. The output circuit of triode 33 may be traced from the lower terminal of secondary winding 25 as it appears in the drawing through a winding 1I of a relay 12, across which a condenser 13 is connected, anode 68 and cathode 10 to a tap suitably located on the secondary winding 25.' The input circuit of triode 33 may be traced from cathode through the upper part of secondary winding and resistance 52 to the control electrode 69.

When a flame is not burning within thecombustion chamber I, the potential drop across resistance 52 is substantially zero and the trlode 33 is maintained substantially non-conductive by the potential impressed on the input circuit e thereof by the upper section of winding 25. When a flame is burning within the combustion chamber, however, a potential drop is produced across resistance 52 as noted hereinbefore, and this potential drop is of the correct polarity to oppose the potential of th'e upper part 'of winding 25 so that the triode 33 is rendered conductive. This effects energization of the relay winding 1I and actuation of a pair of switch arms 13 and 14 from a lower position as seen in the drawing to an upper position. In its lower position switch arm 14 contact 11, and in its upper position it is in engagement with a contact 16. Switch arm 13 is not in engagement with any contact in its lower position but in its upper position isin engagement with a contact 15.

When the temperature of the room or space to be controlled is at its desired value, all parts of the system are in the positions shown in the drawing. and the burner is not in operation.

When the temperature of the room or space falls below the value it is desired to maintain, thermostat I0 operates to move switch arm -I3 against contact I4, thereby completing an energizing circuit for 'the transformer primary winding I6. This energizing traced from line L1 through winding I6, thermal safety switch I5, and thermostat I8 to line L2.

Closure of the thermostat switch arm I3 into engagement with contact I4 also completes energizing circuits for heater coil 22 of thermal is in engagement with a circuit may be 'main operation. It is noted that in the arrangement switch I5, valve 5 and primary 9 of the ignition transformer 8. The energizing circuit for valve 5 and heater coil 22 may be traced from line Li through a conductor 18, 'valve 5, heater coil 22, thermal switch I5, and thermostat I0 to line L2. The circuit through primary winding 9 of the ignition -transformer 8 may be traced from line L1, throughI conductor 18, winding 9, contact 11, switch arm 14, thermal switch I5 and thermostat I0 to line L2.

'I'he normal result of opening valve 5 and energizing the ignition transformer primary winding 9 is the appearance of a flame at the pilot burner 4. The appearance of a flame at the pilot burner is detected by the llame responsive circuit described and effects energization of the relay winding 1I. Energization of winding 1I effects movement of switch arms 13 and 14 into engagement with their upper contacts 15 and 16 respectively and also effects opening of the circuit to the ignition transformer primary winding 9 at contact 11. Movement of switch arm 14 into engagement with' contact 16 closes an energizing circuit for the main valve 3 and movement of switch 13 into engagement with contact 15 closes a shunt circuit about the safety switch heater coil 22. The energizing circuit for valve 3 may be traced from line Ll to conductor 18, valve 3, contact 16, switch arm 14, thermal safety switch I5 and thermostat III to the line L. Normally a flame will subsequently appear at the burner and the system will then be in full illustrated th'e photoelectric cell 62 will then be subjected to light from both the main and pilot burners.

If-the main and pilot burner flames become extinguished while the burner is in operation, the flame responsive circuit will effect de-energization of the relay winding 1I with consequent closing of valve 3 and energization of the thermal safety switch heater coil 22. The ignition transformer 8 will then be re-energized and if a pilot flame does not reappear within a predetermined time depending upon the adjustment of the thermal safety switch, the system will be de-energized by the action of the thermal safety switch under the influence of heater coil 22,

Similarly, if the pilot flame fails to appear during initiation ofthe system operation, relay 1I will not become energized and after a predetermined time the thermal safety switch I5 will operate to de-energize the system.

It may be necessary in some cases to prevent the spark at the ignition electrodes 6 from giving a false indication of th'e presence of a flame. This end may be obtained by positioning the electrodes 6 outside the cone of rays to which the photoelectric cell 62 is subjected or by positioning th'e structure supporting the electrodes 6 between the spark location and the photoelectric cell 62 thereby shielding the latter from the spark.

It will be apparent to those skilled in the art that if desired the pilot burner 4 and its associated valve 5 may be dispensed with. If it is desired to do this, the main valve 3 should be vleft terminal of valve 3 as seen in the drawing to the right hand terminal of the heating resistance 22 instead of to contact 1l. It is noted that in such modification a further reduction of equipment may be eil'ected by connecting the right hand terminal oi resistance 22 to contact 16 whereby the switch ann 13 and contact 'l5 may be dispensed with.

The operation of the safety control system described relies in its operation upon the fact that the illumination and position of the llame in the usual fuel burner fluctuates due to variations in the fuel supply, variations in B. t. u. content of the fuel, and variation in the iiow of combustion supporting air to the burner. With the apparatus described no filters or especially designed optical systems are required to prevent the apparatus from responding to light emanating from the burner walls or other parts within the burner chamber I because the amplier employed responds only to fluctuations in light intensity and does not respond to the comparatively steady light received from the burner walls or other burner parts. The apparatus described has a further advantage that the cone of rays to which the detecting unit is responsive can have a large vertex angle, for example, as shown at 19 in the drawing and can include many objects other than the llame itself and still function satisfactorily.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that in some cases certain features of my invention may sometimes be used to advantage Without a corresponding use of other features.

Having now described my invention, what I ciaim as new and desire to secure by Letters Patent is:

l.. A safety control system for a fuel burner including in combination, means to establish a flame at said burner, relay means to control said first mentioned means having a ilrst position in which said rst mentioned means is permitted to establish a name at said burner and having a second position in which said first mentioned means is prevented from establishing a flame at said burner, and means to control said relay means including a light sensitive device exposed to light from said name, a source of voltage, an eiectric discharge device having an input circuit and an output circuit, a connection between the output circuit of said discharge device and said control means including said voltage source, said control means being adapted to assume its ilrst position when current ilows in said output circuit and being adapted to assume its second position when substantially no current ows therein, a connection between said voltage source and said light sensitive device, and a circuit presenting high resistance to the flow of direct current therethrough but readily passing fluctuating current to electrically couple said last mentioned connection to the input circuit of said discharge device.

2. The combination of claim 1 wherein said light-sensitive device is constructed to respond to substantially all of the radiation within the visible spectrum emanating from said flame.

3. The combination of claim 1 wherein said burner is located within an enclosure and said light sensitive device is also exposed to relatively steady light which emanates from a wall oi' said enclosure.

4. The combination of claim 1 wherein said burner is located within an enclosure and said light sensitive device is constructed to respond to substantially all of the radiation within the visible spectrum emanating from said flame and is also exposed to relatively steady light which emanates from a wall of said enclosure.

5. A safety control system for a fuel burner including in combination, means to establish a. llame at said burner, a device to control said first mentioned means, and means to control said device including a light sensitive device exposed to light from said flame, a source of voltage, an electric discharge device having an input circuit and an output circuit, a connection between the output circuit of said discharge device and said control device including said voltage source, a connection between said voltage source and said light sensitive device, and a circuit presenting high resistance to the flow of direct current therethrough but readily passing fluctuating current to electrically couple said last mentioned connection to the input circuit of said discharge device.

6. A safety control system for a fuel burner including in combination, means to establish a flame at said burner, means to control said ilrst mentioned means, and means to control said control means including a light sensitive device exposed to light from said flame, a source of voltage, an electric discharge device having an input circuit and an output circuit, a connection between the output circuit of said discharge device and said control means including said voltage source, an impedance, a connection including said voltage source, said impedance and said light sensitive device, and a circuit presenting high resistance to the ow of direct current therethrough but readily passing fluctuating current to couple said impedance to the input circuit of said discharge device.

7. 'I'he combination `of claim 6 wherein said light-sensitive device is constructed to respond to substantially all of the radiation within the visible spectrum'emanating from said llame.

8. The combination of claim 6 wherein said burner is located within an enclosure and said light sensitive device is also exposed to relatively steady light which emanates from a wall of said enclosure.

9. The combination of claim 6 wherein said burner is located Within an enclosure and said light sensitive device is constructed to respond to substantially all of the radiation within the visible spectrum emanating from said flame and is also exposed to relatively steady light which emantes from a Wall of said enclosure.

10. A safety control system for a fuel burner including in combination, means to establish a flame at said burner, means to control said ilrst mentioned means, and means to control said control means including a light-sensitive device exposed to light from said llame, a source of voltage, an electric discharge device having an input circuit and an output circuit, a connection between the output circuit of said discharge device and said voltage source including said control means, an impedance, a connection including said voltage source, said impedance and said light-sensitive device, and a circuit having a capacitive reactance therein and presenting high resistance to the flow of direct current therethrough but readily passing fluctuating current to couple said impedance to the input circuit of said discharge device.

11. A safety control system for a fuel burner including in combination, means to establish a flame at said burner, means to control said rst mentioned means, and means to control said controlmeans including a light-sensitive device exposed to light from said llame, a source of voltage, an electric discharge device having an input circuit and an output circuit, a connection between the output circuit of said discharge device and -said voltage source including said l,control means, a second discharge device having an input circuit and an output circuit, reactive means to couple the output circuit of said second discharge device to the input circuit of said ilrst mentioned discharge device, a connection including said voltage source and said light-sensitive device, and a circuit presenting high resistance to the ow of direct current therethrough but readily passing iluctuating current to couple said last mentioned connection to the input circuit of said second discharge device.

12. In combination, a source of illumination, a control device to be adjusted in one sense and in an opposite sense in accordance with the presence and absence respectively of iluctuations in intensity of said source of illumination, a light sensitive device exposed to light from said source, a source of voltage, an', electric discharge device having an input circuit and an output circuit, a connection between the output circuit oi said discharge device and said control device including said voltage source, a connection including said voltage source and said iight sensitive device, and a circuit presenting high resistance to the iiow of direct current therethrough but readily passing iiuctuating current to couple said last mentioned connection to the input circuit o! said discharge device.

13. In combination, a source of illumination, a device to be adjusted in one sense and in 'an opposite sense in accordance with the presence and absence respectively of uctuations in intensity of said source o! illumination, a lightsensitive deviceexposed to light from said source,

a source of voltage, an electric discharge device having an input circuit and an output circuit, a. connection between the output circuit oi said discharge device and said control device including said voltage source, a second discharge device having an input circuit and an output circuit, reactive means to couple the output circuit oi said second discharge device to the input circuit of said first mentioned discharge device, a connection including said voltage current source and said light-sensitive device, and a circuit presenting high resistance to the ilow of direct current therethrough but readily passing fluctuating current to couple ksaid last mentioned connection to the input circuit of said second discharge device.

. including means to establish a flame at said burner, a device to control said means, a source of electrical energy. a circuit connecting said source of energy and said device, and means including alight sensitive device exposed to saidilame to control the conductivity of said circuit and thereby the operation of said device in response to sustained uctuations in the intensity oi' illumination of said ilame, said last mentioned means being insensitive to illumination of steady intensity.

15. A safety control system for a fuel burner including in combination, means to establish a flame at said burner, and means responsive to sustained iluctuations in theintensity oi illumination of lsaid flame but insensitive to illumination of steady 'intensity to control said ilame establishing means.

16. A safety control system for afuel burner including in combination, means to establish a iiame at said burner which flamehas the characteristic of iiuctuating in intensity of illumination, and means including a light sensitive device exposed to the region normally including said name to operate said system in a sense to prevent the presence oi a iiame at said burner when the illumination of said light sensitive device is substantially steady.

' maar s. JONES. 

